The major hypothesis being tested is that a perinatal infection with Reovirus Type III is associated with extrahepatic biliary atresia and idiopathic neonatal hepatitis in infants being evaluated for cholestatic jaundice. We propose to determine if RNA specific for Reovirus can be identified by polymerase chain reaction (PCR) in fresh-frozen liver tissue removed from the bile duct remnant and liver in children with biliary atresia or neonatal hepatitis.